1. Field of the Invention
The present invention concerns a silicone type bonding agent for an optical memory element, an optical memory element, and a method for manufacturing an optical memory element. More specifically, the present invention concerns (a) a silicone type bonding agent for an optical memory element which can be quickly cured by an addition reaction and a condensation reaction, and which makes it possible to bond together in a favorable manner a substrate which has a recording layer on one side and a substrate which may or may not have a recording layer on one side, (b) an optical memory element which is formed by bonding such substrates together in a favorable manner, and (c) a method for the efficient manufacture of such an optical memory element.
2. Description of Related Art
Optical memory elements, such as optical cards or optical disks (video disks or compact disks, etc.), which allow the optical recording, erasing and playback of information, are subject to warping. Warping of the optical memory element is caused by changes in temperature and humidity, etc., and can be alleviated by bonding together two substrates at least one of which has a recording layer on one side. Bonding agents which are used to bond such substrates together include, for example, silicone type optical memory element bonding agents containing a silicone composition which is cured by a two-liquid type condensation reaction (see Japanese Patent Application Kokai No. 61-267947), silicone type optical memory element bonding agents containing a silicone composition which is cured by a de-alcohol type condensation reaction (see Japanese Patent Application Kokai No. 1-276452), and silicone type optical memory element bonding agents containing a silicone composition which is cured by a condensation reaction or an addition reaction (see Japanese Patent Application Kokai No. 3-113744).
Silicone compositions which are cured by a condensation reaction are advantageous in that the curing of such compositions tends to be free of any cure inhibition, so that the abovementioned substrates can be bonded in a favorable manner. However, since curing proceeds gradually from portions of the composition that are in contact with moisture in the air, such compositions suffer from a serious drawback. Such composition must be allowed to stand for a long period of time in order to achieve sufficient curing of the interior portions of the composition sandwiched between the abovementioned substrates such that a fastening force which is sufficient to allow movement of the optical memory element or treatment of the optical memory element in subsequent processes is obtained. Accordingly, continuous bonding of the abovementioned substrates is impossible.
In the case of silicone compositions which are cured by a two-liquid type condensation reaction, curing also proceeds from the interior portions of the silicone composition sandwiched between the abovementioned substrates. Accordingly, problems such as those described above are not encountered to any great extent. However, since curing by the abovementioned condensation reaction proceeds gradually, the optical memory element must be allowed to stand for a long period of time in order to obtain a fastening strength which is sufficient to allow movement or treatment in subsequent processes. Furthermore, in the case of silicone compositions of this type, the adhesion of the composition to the abovementioned substrates tends to be inferior to that seen in the case of single-liquid type silicone compositions, so that it is necessary to subject the abovementioned substrates to a primer treatment beforehand. Accordingly, continuous bonding of the abovementioned substrates is impossible.
In the case of silicone compositions which are cured by an addition reaction, curing also proceeds from the interior portions of the composition sandwiched between the abovementioned substrates, and curing proceeds more rapidly than in the case of silicone compositions cured by a condensation reaction. Accordingly, the time required in order to obtain a fastening strength which is sufficient to allow movement of the optical memory element or treatment of said element in subsequent processes is short, and such compositions are also advantageous in that no by-products are formed during curing. However, curing tends to be inhibited by nitrogen-containing compounds, sulfur-containing compounds, phosphorus-containing compounds, tin-containing compounds and solder flux, etc. Furthermore, the adhesion of compositions of this type to the abovementioned substrates tends to be inferior to that of compositions cured by a condensation reaction, so that it is necessary to subject the substrates to a cleaning treatment or a primer treatment beforehand. Accordingly, continuous bonding of the abovementioned substrates is impossible.
It is an object of the present invention to provide (a) a silicone bonding agent for an optical memory element which can be quickly cured by an addition reaction and a condensation reaction, and which makes it possible to bond together in a favorable manner a substrate which has a recording layer on one side and a substrate which may or may not have a recording layer on one side, (b) an optical memory element which is formed by bonding such substrates together in a favorable manner, and (c) a method for the efficient manufacture of such an optical memory element.